Design of a Compact Active Hip Prosthesis with Human-Like Range of Motion and Torque*

Hip disarticulation and hemipelvectomy are the most severe forms of lower limb amputation, posing significant challenges to prosthetic solutions in terms of size, biomechanical functionality, and user compatibility. While active ankle and knee prostheses have made spectacular progresses recently in restoring a physiological gait, these advancements did not percolate yet to hip prosthesis design. This article introduces an innovative design of an active hip prosthesis displaying remote center of motion, and range of motion and torque compatible with the most ubiquitous locomotion tasks, i.e., walking and stand-to-sit-to-stand transitions. The designed structure incor-porates a tilted double parallelogram mechanism, in order to optimize compactness and minimize internal constraints. The proposed hip prosthesis design features minimal encumbrance, with a horizontal size of 140 mm and a frontal width of 136 mm. Its range of motion spans from -30° to 90°, providing a com-fortable sitting position with existing shell design. Remarkably, the mass of this hip joint is a mere 3.30 kg, excluding battery and power electronics.